1. Field of the Invention
The present invention relates to electrical connectors and, more particularly, to zero-insertion force pin grid array sockets for use in connecting an integrated circuit to a circuit substrate.
2. Brief Description of the Prior Developments
Pin grid array (PGA) sockets are used for connecting an integrated circuit, such as an ASIC (application-specific integrated circuit), to a circuit substrate, such as a printed circuit board. PGA sockets typically comprise a base that supports a plurality of contacts and a cover with insertion holes. The base is mounted on the circuit substrate to form an electrical connection with circuits on the circuit substrate. The cover is attached to the base prior to assembly of the circuit substrate so that the lateral surfaces of the circuit substrate, base and cover are stacked in a parallel arrangement.
When it is desired to connect an IC to the circuit substrate, the pins of the IC are forcibly inserted into the insertion holes of the cover and against the contacts to form an electrical connection there between. The insertion force required to establish an adequate electrical connection is considerable and can lead to difficulty in installing and removing the IC. Moreover, the pins of the IC may be easily damaged as a result of its installation and removal.
Therefore, low insertion force (LIF) and zero insertion force (ZIF) PGA sockets have been developed to reduce the insertion forces needed to establish an electrical interface between the contacts and the pins. The covers of LIF or ZIF PGA sockets are typically attached to the base so that the cover is movable over the lateral surface of the base. A means for camming the cover over the surface of the base so that the contacts are deflected against the pins of the IC is provided. The base cover usually has contact support walls for supporting the individual contacts.
These LIF and ZIF devices, however, also can cause the pins of the ICs to be damaged. For example as the cover moves over the surface of the base, the pins are guillotined against the contacts and, as a result, can be broken or bent. Additionally, the mating force between the contact and the pin may damage the pin since the pins themselves are not provided with any support.
PGA socket covers have rows and columns of insertion holes. The exact number of insertion holes and the orientation of the insertion holes typically depends on the types of ICs to be connected to the circuit substrate. The rows and columns of insertion holes are spaced on 0.1-inch or 0.1-inch interstitial centers to accommodate the pin densities of most ICs available today. However, advancement in technology has resulted in the development of smaller or denser ICs with pins spaced on 0.05-inch centers.
Therefore, there is a need for a PGA socket that can be used to connect an IC to a circuit substrate without damaging the pins of the IC. Moreover, the PGA socket should be compatible with chips having pins spaced on either 0.1-inch or 0.05-inch centers.